1. Field of the Invention
This disclosure relates to polymer resins and, in particular, to adhesion stabilized polymer sheets suitable for use in polymer interlayers, including those utilized in multiple layer panels.
2. Description of Related Art
Polyvinyl butyral (PVB) is often used in the manufacture of polymer sheets that can be used as interlayers in multiple layer panels, including, for example, light-transmitting laminates such as safety glass. PVB is also used in photovoltaic solar panels to encapsulate the panels which are used to generate electricity for commercial and residential applications.
The term “safety glass” generally refers to a transparent laminate that includes at least one polymer sheet, or interlayer, disposed between two rigid substrates, such as, for example, two sheets of glass. Safety glass is often used as a transparent barrier in architectural and automotive applications, and one of its primary functions is to absorb energy resulting from impact and to prevent objects from passing through the laminate. Additionally, even when the applied force is sufficient to break the glass, the polymeric interlayer helps keep the glass bonded to the laminate, which prevents dispersion of sharp glass shards, thereby minimizing injury and damage to people or objects in the vicinity of the glass. Safety glass may also provide other benefits, such as a reduction in ultraviolet (UV) and/or infrared (IR) radiation, and it may also enhance the aesthetic appearance of window openings through addition of color, texture, and the like. Additionally, safety glass with desirable sound insulation properties has also been produced, which results in quieter internal spaces.
The ability of PVB to remain adhered to glass and other inorganic surfaces in a multiple layer panel depends, in part, on the environment in which the panel is utilized during service. In particular, PVB-containing multiple layer panels used in hot and humid environments are susceptible to ingress of moisture, particularly at the edges of the laminate, which may lead to edge delamination. Such delamination reduces the functionality of the panel by adversely impacting its mechanical, optical, and even acoustic performance.
Thus, a need exists for a poly(vinyl acetal) sheet that exhibits enhanced surface adhesion and that can be used in multiple layer panels utilized under a wide range of service conditions, including hot and humid environments, for extended periods of time with steady adhesion. Advantageously, such a sheet could be prepared using existing processing equipment and with minimal additional cost or process steps.